The specific aims of our current research reflect our continued interest in understanding how the doublesex branch of the Drosophila sex determination hierarchy functions to direct growth, morphogenesis, and differentiation to build into individuals the potential for adult sexual functions. We also want to understand how information from the sex determination hierarchy is integrated with information from pattering hierarchies, in particular the HOX genes, to govern development and differentiation. We are addressing the following topics: I. How is genital imaginal disc development controlled? Our immediate goals are to: (A) understand how the functioning of the major regulatory hierarchies patterning the third instar genital disc is integrated; (B) characterize additional genes we have identified that are expressed sex-specifically or segment-specifically in the genital disc, with a strong emphasis on events likely to be immediately downstream of dsx; (C) identify direct DSX targets. II. Both the doublesex and fruitless branches of the sex hierarchy are active in gustatory sense organs on the male foreleg. We will elucidate how the two branches of the sex hierarchy act together to generate sex-specific aspects of the gustatory sensory system. III. We will test whether the female-specific doublesex protein specifies the circuitry for female sexual behavior in the nervous system. If it does, as seems likely from extant data, then we will dissect (A) how the potential for innate female sexual behaviors is built into the nervous system during development and (B) how the circuitry underlying those behaviors functions in an adult. The genes at the bottoms of the D. melanogaster sex hierarchy (doublesex and probably intersex) are evolutionarily conserved through insects to vertebrates, including human, and doublesex also functions in sexual development in mice and humans. Thus studies such as ours will provide models for understanding aspects of the fundamental biological process of sexual development. Elucidating how innate behaviors are built into nervous systems during development may provide groundbreaking insights into vast areas of nervous system development and function. [unreadable] [unreadable] [unreadable]